Circuits and methods for heating batteries in series using resonance components in series

ABSTRACT

Certain embodiments of the present invention provide a battery heating circuit, wherein: the battery comprises a first battery E 1  and a second battery E 2,  the heating circuit comprises a first switch unit  10,  a second switch unit  20,  a damping component R 1,  a damping component R 2,  a current storage component L 1,  a current storage component L 2,  a switching control module  100  and a charge storage component C; the first battery, the damping component R 1,  the current storage component L 1,  the first switch unit  10  and the charge storage component C are connected in series to form a first charging/discharging circuit; the second battery, the damping component R 2,  the current storage component L 2,  the charge storage component C and the second switch unit  20  are connected in series to form a second charging/discharging circuit.

1. CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation-in-part of U.S. patent application Ser.No. 13/189,114, which claims priority to Chinese Patent Application No.201010245288.0, filed Jul. 30, 2010, Chinese Patent Application No.201010274785.3, filed Aug. 30, 2010, and Chinese Patent Application No.201010604744.6, filed Dec. 23, 2010, all these four applications beingincorporated by reference herein for all purposes.

Additionally, this application is related to International ApplicationPublication No. WO2010/145439A1 and Chinese Application Publication No.CN102055042A, both these two applications being incorporated byreference herein for all purposes.

2. BACKGROUND OF THE INVENTION

The present invention pertains to electric and electronic field, inparticular related to a battery heating circuit.

Considering cars need to run under complex road conditions andenvironmental conditions or some electronic devices are used under harshenvironmental conditions, the battery, which serves as the power supplyunit for electric-motor cars or electronic devices, need to be adaptiveto these complex conditions. In addition, besides these conditions, theservice life and charge/discharge cycle performance of the battery needto be taken into consideration; especially, when electric-motor cars orelectronic devices are used in low temperature environments, the batteryneeds to have outstanding low-temperature charge/discharge performanceand higher input/output power performance.

Usually, under low temperature conditions, the resistance of the batterywill increase, and so will the polarization; therefore, the capacity ofthe battery will be reduced.

To keep the capacity of the battery and improve the charge/dischargeperformance of the battery under low temperature conditions, someembodiments of the present invention provide a battery heating circuit.

3. BRIEF SUMMARY OF THE INVENTION

The objective of certain embodiments of the present invention is toprovide a battery heating circuit, in order to solve the problem ofdecreased capacity of the battery caused by increased resistance andpolarization of the battery under low temperature conditions.

Certain embodiments of the present invention provide a battery heatingcircuit, wherein: the battery comprises a first battery and a secondbattery, the heating circuit comprises a first switch unit, a secondswitch unit, a damping component R1, a damping component R2, a currentstorage component L1, a current storage component L2, a switchingcontrol module and a charge storage component C; the first battery, thedamping component R1, the current storage component L1, the first switchunit and the charge storage component C are connected in series to forma first charging/discharging circuit; the second battery, the dampingcomponent R2, the current storage component L2, the charge storagecomponent C and the second switch unit are connected in series to form asecond charging/discharging circuit; when the charge storage component Cis charged or discharges, the direction of charging/discharging currentin the second charging/discharging circuit is opposite to the directionof charging/discharging current in the first charging/dischargingcircuit; the switching control module is electrically connected with thefirst switch unit and second switch unit, and is configured to controlthe first switch unit and the second switch unit to switch onalternately, so as to control the electric energy to flow between thefirst battery, the charge storage component C and the second battery.

In the heating circuit provided in certain embodiments of the presentinvention, the first switch unit and the second switch unit can becontrolled by the switching control module to switch on alternately, sothat the electric energy can flow back-and-forth between the firstbattery, the charge storage component C and the second batteryalternately, and thereby causes the damping component R1 and the dampingcomponent R2 to generate heat, so as to heat up the first battery andthe second battery. For example, since the direction ofcharging/discharging current in the second charging/discharging circuitis opposite to the direction of charging/discharging current in thefirst charging/discharging circuit when viewed from the perspective ofthe charge storage component C, the energy that is transferred from thefirst battery into the charge storage component C can be transferredsuccessfully to the second battery, so that the heating efficiency isimproved.

In the heating circuit provided in certain embodiments of the presentinvention, the charge storage component is connected with the batteriesin series; when the batteries are heated, safety problems related withfailure or short circuit of the switch unit can be avoided due to theexistence of the charge storage component, and therefore the batteriescan be protected effectively.

Other characteristics and advantages of the present invention will befurther described in detail in the following section for embodiments.

4. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, as a part of this description, are providedhere to facilitate further understanding of the present invention, andare used in conjunction with the following embodiments to explain thepresent invention, but shall not be comprehended as constituting anylimitation on the present invention. In the figures:

FIG. 1 is a schematic diagram showing a battery heating circuitaccording to one embodiment of the present invention;

FIG. 2 is a timing diagram of waveforms of the heating circuit as shownin FIG. 1 according to one embodiment of the present invention;

FIG. 3 is a schematic diagram showing a battery heating circuitaccording to another embodiment of the present invention;

FIG. 4 is a timing diagram of waveforms of the heating circuit as shownin FIG. 3 according to another embodiment of the present invention;

FIG. 5 is a schematic diagram showing a battery heating circuitaccording to yet another embodiment of the present invention;

FIG. 6 is a timing diagram of waveforms of the heating circuit as shownin FIG. 5 according to yet another embodiment of the present invention;and

FIG. 7 is a schematic diagram showing the first switch unit and/or thesecond switch unit as part of the battery heating circuit as shown inFIG. 1, FIG. 3, and/or FIG. 5 according to certain embodiments of thepresent invention.

5. DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the present invention are described in detailbelow, with reference to the accompanying drawings. It should beappreciated that the embodiments described here are only provided todescribe and explain the present invention, but shall not be deemed asconstituting any limitation on the present invention.

It is noted that, unless otherwise specified, when mentioned hereafterin this description, the term “switching control module” may refer toany controller that can output control commands (e.g., pulse waveforms)under preset conditions or at preset times and thereby control theswitch unit connected to it to switch on or switch off accordingly,according to some embodiments. For example, the switching control modulecan be a PLC. Unless otherwise specified, when mentioned hereafter inthis description, the term “switch” may refer to a switch that enablesON/OFF control by using electrical signals or enables ON/OFF control onthe basis of the characteristics of the component according to certainembodiments. For example, the switch can be either a one-way switch(e.g., a switch composed of a two-way switch and a diode connected inseries, which can be conductive in one direction) or a two-way switch(e.g., a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) oran IGBT with an anti-parallel freewheeling diode). Unless otherwisespecified, when mentioned hereafter in this description, the term“two-way switch” may refer to a switch that can be conductive in twodirections, which can enable ON/OFF control by using electrical signalsor enable ON/OFF control on the basis of the characteristics of thecomponent according to some embodiments. For example, the two-way switchcan be a MOSFET or an IGBT with an anti-parallel freewheeling diode.Unless otherwise specified, when mentioned hereafter in thisdescription, the term “one-way semiconductor component” may refer to asemiconductor component that can be conductive in one direction, such asa diode, according to certain embodiments. Unless otherwise specified,when mentioned hereafter in this description, the term “charge storagecomponent” may refer to any device that can enable charge storage, suchas a capacitor, according to some embodiments. Unless otherwisespecified, when mentioned hereafter in this description, the term“current storage component” may refer to any device that can storecurrent, such as an inductor, according to certain embodiments. Unlessotherwise specified, when mentioned hereafter in this description, theterm “forward direction” may refer to the direction in which the energyflows from the battery to the energy storage circuit, and the term“reverse direction” may refer to the direction in which the energy flowsfrom the energy storage circuit to the battery, according to someembodiments. Unless otherwise specified, when mentioned hereafter inthis description, the term “battery” may comprise primary battery (e.g.,dry battery or alkaline battery, etc.) and secondary battery (e.g.,lithium-ion battery, nickel-cadmium battery, nickel-hydrogen battery, orlead-acid battery, etc.), according to certain embodiments. Unlessotherwise specified, when mentioned hereafter in this description, theterm “damping component” may refer to any device that inhibits currentflow and thereby enables energy consumption, such as a resistor, etc.,according to some embodiments. Unless otherwise specified, whenmentioned hereafter in this description, the term “main loop” may referto a loop composed of battery, damping component, switch unit and energystorage circuit connected in series according to certain embodiments.

It should be noted specially that, considering different types ofbatteries have different characteristics, in some embodiments of thepresent invention, “battery” may refer to an ideal battery that does nothave internal parasitic resistance and parasitic inductance or has verylow internal parasitic resistance and parasitic inductance, or may referto a battery pack that has internal parasitic resistance and parasiticinductance; therefore, those skilled in the art should appreciate thatif the battery is an ideal battery that does not have internal parasiticresistance and parasitic inductance or has very low internal parasiticresistance and parasitic inductance, the damping component R1 may referto a damping component external to the battery and the current storagecomponent L1 may refer to a current storage component external to thebattery; if the battery is a battery pack that has internal parasiticresistance and parasitic inductance, the damping component R1 may referto a damping component external to the battery or refer to the parasiticresistance in the battery pack, and the current storage component L1 mayrefer to a current storage component external to the battery or refer tothe parasitic inductance in the battery pack, according to certainembodiments.

To ensure the normal service life of the battery, according to someembodiments, the battery can be heated under low temperature condition,which is to say, when the heating condition is met, the heating circuitis controlled to start heating for the battery; when the heating stopcondition is met, the heating circuit is controlled to stop heating,according to certain embodiments.

In the actual application of battery, the battery heating condition andheating stop condition can be set according to the actual ambientconditions, to ensure normal charge/discharge performance of thebattery, according to some embodiments.

FIG. 1 is a schematic diagram showing a battery heating circuitaccording to one embodiment of the present invention. As shown in FIG.1, one embodiment of the present invention provides a battery heatingcircuit, wherein: the battery comprises a first battery E1 and a secondbattery E2, the heating circuit comprises a first switch unit 10, asecond switch unit 20, a damping component R1, a damping component R2, acurrent storage component L1, a current storage component L2, aswitching control module 100 and a charge storage component C; the firstbattery E1, damping component R1, current storage component L1, firstswitch unit 10 and charge storage component C are connected in series toform a first charging/discharging circuit; the second battery E2,damping component R2, current storage component L2, charge storagecomponent C and second switch unit 20 are connected in series to form asecond charging/discharging circuit; when the charge storage component Cis charged or discharges, the direction of charging/discharging currentin the second charging/discharging circuit is opposite to the directionof charging/discharging current in the first charging/dischargingcircuit; the switching control module 100 is electrically connected withthe first switch unit 10 and second switch unit 20, and is configured tocontrol the first switch unit 10 and second switch unit 20 to switch onalternately, so as to control the electric energy flow between the firstbattery E1, charge storage component C and second battery E2.

Wherein: the switching control module 100 can control the first switchunit 10 and second switch unit 20 to switch on or off, for example, thefirst switch unit 10 switches from ON state to OFF state, while thesecond switch unit 20 switches from OFF state to ON state, so that theelectric energy stored in the charge storage component C from onebattery can flow into the other battery. As the electric energy flows,current is generated; by keeping current flowing through the dampingcomponent R1 and damping component R2 continuously, the dampingcomponent R1 and damping component R2 generate heat, and thereby heat upthe first battery E1 and second battery E2.

FIG. 2 is a timing diagram of waveforms of the heating circuit as shownin FIG. 1 according to one embodiment of the present invention.Hereunder the working process of the heating circuit provided in oneembodiment of the present invention will be described, with reference toFIG. 2. First, the switching control module 100 controls the firstswitch unit 10 to switch on, and controls the second switch unit 20 toswitch off; the first battery E1, the damping component R1, the currentstorage component L1, the first switch unit 10 and the charge storagecomponent C form a charging/discharging circuit, which performscharging/discharging operations (as indicated by the time periods t1˜t2as shown in FIG. 2, wherein: the time period t1 represents the chargingtime period of the charging/discharging circuit; at the end of the timeperiod t1, the capacitive voltage U_(C) of the charge storage componentC is at the peak value of the positive half cycle, and the capacitivecurrent I_(C) reaches zero after the positive half cycle; the timeperiod t2 represents the discharging time period of thecharging/discharging circuit). After a charging/discharging cycle iscompleted (at this point, the current k through the charge storagecomponent C reaches zero after the negative half cycle), the switchingcontrol module 100 controls the first switch unit 10 to switch off, andcontrols the second switch unit 20 to switch on; the second battery E2,the damping component R2, the current storage component L2, the chargestorage component C, and the second switch unit 20 form acharging/discharging circuit, which performs charging/dischargingoperations (as indicated by the time periods t3˜t4 as shown in FIG. 2,wherein: the time period t3 represents the charging time period of thecharging/discharging circuit, while the time period t4 represents thedischarging time period of the charging/discharging circuit). After thecharging/discharging circuit completes a charging/discharging cycle (atthis point, the current I_(C) through the charge storage component Creaches zero after the positive half cycle, and the entire heatingcircuit completes a complete working cycle), the switching controlmodule 100 controls the first switch unit 10 to switch on and controlsthe switch unit 20 to switch off again; in that way, the cycles continueon, so that the current flows through the damping component R1 and thedamping component R2 continuously; as a result, the damping component R1and the damping component R2 generate heat, and thereby heat up thefirst battery E1 and the second battery E2 until the heating process iscompleted.

In the above working process of the heating circuit provided in certainembodiments of the present invention, the current can be kept flowingback-and-forth between the first battery E1 and the second battery E2,so that two batteries are heated up alternately, and therefore theheating efficiency is improved.

FIG. 3 is a schematic diagram showing a battery heating circuitaccording to another embodiment of the present invention. Preferably, asshown in FIG. 3, the heating circuit provided in one embodiment of thepresent invention further comprises a current storage component L10 anda current storage component L20, wherein: the current storage componentL10 is connected in series in the first charging/discharging circuit,and the current storage component L20 is connected in series in thesecond charging/discharging circuit. Thereby, the current storagecomponent L10 and current storage component L20 can be utilized toimplement current limiting for the capacitive current I_(C) (i.e., thecurrent flow through the first and second batteries and the first andsecond switch units) in both directions, so as to decrease the magnitudeof current flowing through the first and second batteries and the firstand second switch units, and attain the purpose of protecting the firstand second batteries and the first and second switch units.

FIG. 4 is a timing diagram of waveforms of the heating circuit as shownin FIG. 3 according to another embodiment of the present invention. Asshown in FIG. 4, compared to the capacitive current I_(C) as shown inFIG. 2, the capacitive current I_(C) as shown in FIG. 4 has a smootherwaveform, with a peak value and a valley value much smaller than thepeak value and the valley value of the capacitive current I_(C) as shownin FIG. 2, respectively.

FIG. 5 is a schematic diagram showing a battery heating circuitaccording to yet another embodiment of the present invention.Preferably, as shown in FIG. 5, the heating circuit provided in oneembodiment of the present invention can further comprise a currentstorage component L10, a current storage component L20, a one-waysemiconductor component D1, a one-way semiconductor component D2, aone-way semiconductor component D10 and a one-way semiconductorcomponent D20, wherein: the one-way semiconductor component D10 isconnected in series with the first switch unit 10, the current storagecomponent L10 and one-way semiconductor component D1 connected in serieswith each other are connected in parallel between the ends of theone-way semiconductor component D10 and first switch unit 10 connectedin series with each other, so as to limit the current in the firstcharging/discharging circuit in reverse direction; and, the one-waysemiconductor component D20 is connected in series with the secondswitch unit 20, and the current storage component L20 and one-waysemiconductor component D2 connected in series with each other areconnected in parallel between the ends of the one-way semiconductorcomponent D20 and second switch unit 20 connected in series with eachother, so as to limit the current in the second charging/dischargingcircuit in reverse direction. Thereby, the capacitive current (i.e.,current flowing through the first battery E1 and second battery E2) islimited in one direction (i.e., current limiting during charging of thefirst battery E1 and second battery E2). Thus, compared to the heatingcircuit (two-way current limiting) in the second embodiment, the heatingcircuit here can further improve the heating efficiency on the premiseof protecting the first and second batteries and the first and secondswitch units.

FIG. 6 is a timing diagram of waveforms of the heating circuit as shownin FIG. 5 according to yet another embodiment of the present invention.As shown in FIG. 6, compared to the capacitive current I_(C) as shown inFIG. 4, the capacitive current I_(C) as shown in FIG. 6 has a higherpeak value in the positive half cycle.

FIG. 7 is a schematic diagram showing the first switch unit and/or thesecond switch unit as part of the battery heating circuit as shown inFIG. 1, FIG. 3, and/or FIG. 5 according to certain embodiments of thepresent invention. As shown in FIG. 7, the first switch unit 10 and/orthe second switch unit 20 can comprise a switch K11 and a one-waysemiconductor component D11 connected in parallel with the switch K11 inreverse direction, wherein: the switching control module 100 iselectrically connected with the switch K11, and is configured to controlON/OFF of the forward direction branches of the first switch unit 10and/or the second switch unit 20 by controlling ON/OFF of the switchK11. The ON/OFF control of switch K11 can be performed in the grid zoneas shown in FIG. 2, FIG. 4 and FIG. 6. When or after the current flowthrough the first switch unit 10 or the second switch unit 20 reacheszero, the switching control module 100 can control the first switch unit10 or second switch unit 20 to switch off.

The heating circuit provided in certain embodiments of the presentinvention has the following advantages:

(1) When viewed from the aspect of the charge storage component, thedirection of the charging/discharging current in the secondcharging/discharging circuit is opposite to the direction of thecharging/discharging current in the first charging/discharging circuit;therefore, the electric energy can flow back-and-forth between the firstbattery, the charge storage component and the second batteryalternately, and thereby the resultant current causes the dampingcomponent R1 and the damping component R1 to generate heat, so that thefirst battery and the second battery are heated up; in that way, thefirst battery and the second battery are heated alternately, and theheating efficiency is high;

(2) Since the current storage component provides the current limitingfunction and only one charging/discharging circuit is formed in eachtime period, the current flowing through the first battery and thesecond battery and the current flowing through the first switch unit andthe second switch unit are lower; in addition, due to the structure ofthe charging/discharging circuit and the existence of the currentstorage components L10 and L20, the current flowing through the firstbattery and the second battery and the current flowing through the firstswitch unit and the second switch unit can be further limited, so as toavoid damage to the batteries and the switch units resulted from largecurrents;

(3) With the one-way current limiting scheme, the discharging efficiencyof the first battery and the second battery is improved, and thecharging current in reverse direction is limited to prevent damage tothe first battery and the second battery; therefore, the first batteryand the second battery and the switch units are protected againstdamage, and the heating efficiency is improved; and/or

(4) In the heating circuit provided in some embodiments of the presentinvention, the charge storage component is connected with the batteriesin series; when the batteries are heated, safety problems related withfailure or short circuit of the switch units can be avoided due to theexistence of the charge storage component, and therefore the batteriescan be protected effectively.

Certain embodiments of the present invention provide a battery heatingcircuit, wherein: the battery comprises a first battery E1 and a secondbattery E2, the heating circuit comprises a first switch unit 10, asecond switch unit 20, a damping component R1, a damping component R2, acurrent storage component L1, a current storage component L2, aswitching control module 100 and a charge storage component C; the firstbattery, the damping component R1, the current storage component L1, thefirst switch unit 10 and the charge storage component C are connected inseries to form a first charging/discharging circuit; the second battery,the damping component R2, the current storage component L2, the chargestorage component C and the second switch unit 20 are connected inseries to form a second charging/discharging circuit; when the chargestorage component C is charged or discharges, the direction of thecharging/discharging current in the second charging/discharging circuitis opposite to the direction of the charging/discharging current in thefirst charging/discharging circuit; the switching control module 100 iselectrically connected with the first switch unit 10 and the secondswitch unit 20, and is configured to control the electric energy flowbetween the first battery E1, the charge storage component C and thesecond battery E2. The battery heating circuit of certain embodiments ofthe present invention can achieve high heating efficiency.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. In another example,some or all components of various embodiments of the present inventioneach are, individually and/or in combination with at least anothercomponent, implemented in one or more circuits, such as one or moreanalog circuits and/or one or more digital circuits.

While some embodiments of the present invention are described above withreference to the accompanying drawings, the present invention is notlimited to the details of those embodiments. Those skilled in the artcan make modifications and variations, without departing from the spiritof the present invention. However, all these modifications andvariations shall be deemed as falling into the scope of the presentinvention.

In addition, it should be noted that the specific technical featuresdescribed in the above embodiments can be combined in any appropriateway, provided that there is no conflict. To avoid unnecessaryrepetition, certain possible combinations are not describedspecifically. Moreover, the different embodiments of the presentinvention can be combined as needed, as long as the combinations do notdeviate from the spirit of the present invention. However, suchcombinations shall also be deemed as falling into the scope of thepresent invention.

Hence, although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

What is claimed is:
 1. A circuit for heating a first battery and asecond battery, the circuit comprising: the first battery including afirst damping component and a first current storage component, the firstdamping component and the first current storage component beingparasitic to the first battery; the second battery including a seconddamping component and a second current storage component, the seconddamping component and the second current storage component beingparasitic to the second battery; a first switch unit; a second switchunit; a switching control component coupled to the first switch unit andthe second switch unit; and a charge storage component; wherein: thefirst battery, the first switch unit, and the charge storage componentare connected to form a first charging and discharging circuit; and thesecond battery, the second switch unit, and the charge storage componentare connected to form a second charging and discharging circuit;wherein: the switching control component is configured to turn on thefirst switch unit and the second switch unit alternately so as tocontrol a first current flowing between the first battery and the chargestorage component and a second current flowing between the secondbattery and the charge storage component; and the circuit for heatingthe first battery and the second battery is configured to heat the firstbattery and the second battery by at least discharging the first batteryand discharging the second battery.
 2. The circuit of claim 1 whereinthe circuit for heating the first battery and the second battery isfurther configured to charge the charge storage component with the firstcurrent flowing in a first direction and with the second current flowingin a second direction, the first direction and the second directionbeing opposite to each other.
 3. The circuit of claim 1 wherein: thefirst damping component is a first parasitic resistor of the firstbattery; the first current storage component is a first parasiticinductor of the battery; the second damping component is a secondparasitic resistor of the second battery; and the second current storagecomponent is a second parasitic inductor of the battery.
 4. The circuitof claim 3 wherein the charge storage component is a capacitor.
 5. Thecircuit of claim 1 and further comprising: a third current storagecomponent connected in series with the first battery and the firstswitch unit; and a fourth current storage component connected in serieswith the second battery and the second switch unit; wherein: the firstcharging and discharging circuit includes the third current storagecomponent; and the second charging and discharging circuit includes thefourth current storage component.
 6. The circuit of claim 5 wherein eachof the third current storage component and the fourth current storagecomponent is an inductor.
 7. The circuit of claim 1 and furthercomprising: a first one-way semiconductor component connected in serieswith the first battery and the first switch unit; and a second one-waysemiconductor component connected in series with the second battery andthe second switch unit.
 8. The circuit of claim 1 and furthercomprising: a third one-way semiconductor component; a third currentstorage component connected in series with the third one-waysemiconductor component; a fourth one-way semiconductor component; and afourth current storage component connected in series with the fourthone-way semiconductor component.
 9. The circuit of claim 8 wherein: acombination of the third one-way semiconductor component and the thirdcurrent storage component is parallel to a combination of the firstone-way semiconductor component and the first switch unit; and acombination of the fourth one-way semiconductor component and the fourthcurrent storage component is parallel to a combination of the secondone-way semiconductor component and the second switch unit.
 10. Thecircuit of claim 9 wherein: the third one-way semiconductor componentand the third current storage component are configured to limit thefirst current if the first current flows from the charge storagecomponent to the first battery; and the fourth one-way semiconductorcomponent and the fourth current storage component are configured tolimit the second current if the second current flows from the chargestorage component to the second battery.
 11. The circuit of claim 8wherein each of the third current storage component and the fourthcurrent storage component is an inductor.
 12. The circuit of claim 1wherein: the first switch unit includes a first switch and a firstone-way semiconductor component connected in parallel with the firstswitch; and the switching control component is coupled to the firstswitch and configured to turn on and off the first switch respectively.13. The circuit of claim 12 wherein: the second switch unit includes asecond switch and a second one-way semiconductor component connected inparallel with the second switch; and the switching control component iscoupled to the second switch and configured to turn on and off thesecond switch respectively.
 14. The circuit of claim 1 wherein theswitching control component is configured to, if the first currentflowing from the charge storage component to the first battery becomeszero, turn off the first switch unit and turn on the second switch unit.15. The circuit of claim 14 wherein the switching control component isconfigured to, if the second current flowing from the charge storagecomponent to the second battery becomes zero, turn off the second switchunit and turn on the first switch unit.
 16. The circuit of claim 1 isfurther configured to: start heating the first battery and the secondbattery if at least one heating start condition is satisfied; and stopheating the first battery and the second battery if at least one heatingstop condition is satisfied.